Leuco phthalocyanine and diazo compound in photographic element



United States Patent '0 LEUCO PHTHALOCYANINE AND DIAZO COM- POUND IN PHOTOGRAPHIC ELEMENT Ren Robert Zemp, East Brunswick Township, Middlesex County, N.J., assignor to E. I. du Pont de Nemours and Company, Wilmington, Del., a corporation of Delaware No Drawing. Application April 6, 1955 Serial No. 499,753

9 Claims. (Cl. 96-49) This invention relates to photography and more particularly to a process for producing photographic images in the form of phthalocyanine pigments. The invention also relates to photographic elements, e.g., films, foils, plates or papers having at least one light-sensitive stratum comprising a solvent-soluble phthalocyanine intermediate complex.

An object of this invention is to provide a new process for producing photographic images in the form of an insoluble phthalocyanine pigment. A more specific object is to provide a new process for producing photographic images in the form of an insoluble metal phthalocyanine pigment. Another object is to provide such a process which is simple and dependable. A further object is to provide new photographic elements which can be readily processed to yield insoluble phthalocyanine pigment images. Still other objects will be apparent from the following description of the invention.

It has been found that photosensitive elements can be prepared by applying on the surface of a suitable support, e. g., a self-supporting film, foil, plate, paper or cloth, or a laminated sheet made of one or more of such materials, an organic solvent solution of a solvent-soluble phthalocyanine intermediate complex (hereinafter sometimes referred to as a leuco-phthalocyanine) and a diazonium compound which yields a reducing agent on exposure to light selected from the group consisting of 1,2- and 1,4- aminohydroxyand dihydroxy-benzenes and naphthalenes and drying the resultant layer.

If desired, the surface of the support, particularly if it has hydrophobic properties, can be provided with a layer of a water-permeable colloid, e.g., gelatin, polyvinyl alcohol, a polyvinyl acetal, etc. Such a layer will absorb or imbibe the solution of the complex and the diazonium compound and, upon processing the element, will serve as a carrier for the resulting photographic image.

The solvent solution of solvent-soluble phthalocyanine intermediate complex and the diazonium compound can be admixed with an aqueous solution or dispersion of a Water-permeable colloid and the resulting dispersion coated on the surface of a support to form a photosensitive layer, which is dried.

The photosensitive element is exposed through 'a suitable continuous tone, halftone, or line negative to a source of actinic light and treated (a) with a solvent for the leuco-phthalocyanine or (b) with a solution of a strong acid containing water whereby a positive image in the form of a metal phthalocyanine pigment is produced. The image-bearing element is then washed with water and dried.

One type of solvent-soluble phthalocyanine intermediate complex, which has been defined as a precursor, is believed to consist of 1.5 molecules of phthalocyanine, the half molecule being perpendicular in spacial relation- :ship to the planar structure of the basic phthalocyanine molecule. This complex or precursor has the empirical formula Q(C H N NH in which each of the six C H N groups represents one phthalonitrile unit, four of which "ice are joined to Q which is two hydrogen atoms (imino) or a central bivalent metal taken from the group consisting of Ni and Cu and form a metal-free or metal phthalocyanine molecule, the two extra phthalonitrile units and the extra NH group representing the precursor Wing" (C H N NH, said complex being further characterized by yielding a metal-free, or a nickel or copper phthalocyanine upon being treated with reducing agents, the remaining two units of phthalonitrile and the extra NH group being split off in the process and in the form of an ammonia and phthalonitrile or other phthalic compounds resulting from the interaction of phthalonitrile, ammonia and the reducing medium. Considering that the metal-phthalocyanine molecule generally consists of 4 phthalonitrile units joined together to a central bivalent metal atom, it is clear that the metal phthalocyanine precursors embrace in their structure a molecule of a metal phthalocyanine plus two extra phthalonitrile units and an extra NH group. This type of complex and processes of preparing various complexes are described in Barnhart and Skiles U. S. application Ser. No. 252,401, filed October 20, 1951 (US. Patent 2,772,284, patented November 27, 1956), and in French Patent 1,068,092, dlivr February 3, 1954, and Brooks French Patent 1,094,376, dlivr December 8, 1954. These solvent-soluble phthalocyanine intermediate complexes are obtained by reacting, in an alcoholic solvent, a phthalonitrile, ammonia and an anhydrous salt of a metal of the group consisting of copper and nickel, said complexes being characterized by yielding upon reduction a metal phthalocyanine, a phthalonitrile and ammonia.

Another type of solvent-soluble phthalocyanine intermediate complex, more specifically defined as a propigment, can be represented by the formula:

MPc\ wherein MPc designates the phthalocyanine compound of the group consisting of metal phthalocyanines and metal-free phthalocyanines, X is a halogen selected from the group consisting of chlorine and bromine, R is an alkyl group and n is 'a subscript not less than 1 and not greater than 4. Of the metal phthalocyanines other than copper phthalocyanine which may be used are those of Co, Ni, Cr, Fe, Mg and Na.

Yet another type of solvent-soluble phthalocyanine propigment can be represented by the formula:

/OCOR MPO O-COR wherein MPc designates the molecule of a phthalocyanine compound of the group consisting of metal-phthalocyanines and metal-free phthalocyanine, while COR designates the acyl radical of an organic carboxylic acid having a total of not less than 2 and not more than 7 carbon atoms in the latter two structural formulae, in the case of the metal-free phthalocyanine compounds M is two hydrogen atoms, and in the case of the metal phthalocyanines M is a metal, i.e., one the above mentioned divalent metals, e.g., Cu or Ni.

The above propigments and detailed methods of preparing them are described in Pedersen U. S. Patents 2,662,895, 2,662,896 and 2,662,897.

Each of the solvent-soluble phthalocyanine intermediate complexes described above, for convenience, have been referred to as leuco-phthalocyanines, by analogy to the term employed in the vat dye field, it being remembered, however, that whereas a leuco vat compound is a reduction product of the dye, the leuco-phthalocyanines are in a sense a higher oxidation stage than the corresponding phthalocyanines, inasmuch as they yield the latter upon treatment with reducing agents.

These leuco-phthalocyanines are essentially colorless as compared with the insoluble parent phthalocyanines (which have an intense reddish-blue to greenish-blue color). The leuco-phthalocyanines are barely colored (producing in solution a yellow-brown, or reddish-brown or violet color) and they have no tinctorial value.

As compared with the generally highly insoluble phthalocyanine parent materials, the leucophthalocyanines are readily soluble in common organic solvents, e.g., methanol, ethanol, chloroform, acetone, 2-ethoxy ethanol, dioxane; ethylene glycol monomethyl, monoethyl or monobutyl ether; benzene, toluene, and the xylenes, but they are insoluble in water.

While the exact nature of the colorant-producing reaction is not known, it is believed that the diazonium compound is decomposed under the influence of light, e.g., ultraviolet light, to form a reducing compound which in turn reduces the leuco-phthalocyanine (precursor or propigment). In general, the diazonium compound is used in molecular excess. Good results can be obtained with 0.5 to 5.0 mols of the diazonium compound per mol of leuco-phthalocyanine.

Among the useful diazonium compounds are diazotized:

p-Aminodimethylaniline p-Aminodiethylaniline 1-amino-2-diethylaminobenzene l-methyl-2-diethylamino-S-aminobenzene 1-amino-3-dimethylaminobenzene 2-amino-n-methyl-diphenylamine 1,4-diaminobenzene N- (4-aminophenyl -morpholine N-(4-aminophenyl)-piperidine 1-(4-aminophenyl) -pyrrolidine 4-amino-2-methoxy-1-cyclohexyl-aminobenzene 4-diethylamino-l-aminonaphthalene Z-methylamino-l-aminonaphthalene 4-phenylamino-3-methyll-aminonaphthalene 4-amiuo-l-naphthol These compounds are employed in the form of their salts and preferred salts are sulfates, chlorides and fluoborates. These compounds may contain various inocuous groups or substituents in the benzene or naphthalene nuclei, including 'alkyl, e.g., methyl, ethyl, isopropyl; aryl, e.g., phenyl; halogen, e.g., chlorine and bromine; alkoxy, e.g., methoxy, ethoxy, etc. groups. Useful diazonium salts on photoreduction produce reducing agents whose redox potentials lie between about 0.877 and +0.50 volt.

Prior to use, the photosensitive solutions and photosensitive elements should be kept under conditions of darkness and during use should not be exposed to any significant amount of actinic light. The usual dark-room safelights can be used to prevent undesirable exposure.

The period of exposure will, of course, depend upon the intensity of the light source, the particular leucophthalocyanine and the particular reducing agent. In general, a period of 0.5 to 20 minutes is required to give an image of satisfactory intensity.

Removal. of the leuco-phthalocyanine from the unexposed are-as and underexposed portions of the original photosensitive layer can be accomplished by the use of any solvent for the l-euco-phthalocyanine. When acids are used in the bath for removing the unexposed areas, a variety of aqueous acid solutions can be used. Suitable such acids include hydrochloric, sulfuric, nitric, phosphoric, acetic and formic; non-oxidizing acids are preferred. The solutions may contain 5% to 50% or more by weight based on the water of a water-soluble alcohol, e.g., methanol or ethanol. In general, the acids are useful in concentrations of 5 to 50% by weight in water. The

non-oxidizing acids have a further function, namely, they brighten the final color.

The invention will be further illustrated but is not intended to be limited by the following examples.

Example I Twenty-five cc. of a 1% by weight solution of the copper phthalocyanine propigment described in U. S. Patent 2,662,897 in ethanol were mixed with 25 cc. of a 1% by weight solution of 1-methyl-2-diethylamino-benzene-S-diazonium fluoborate in ethanol. A sheet of filter paper was dipped in this solution and dried at room temperature. All operations were carried out under orange light. The sensitized paper was exposed to the light of a watt mercury vapor lamp at a distance of 30 cm. for 10 minutes. Part of the paper was covered with a metal strip during this exposure. The exposed paper was treated with ethanol in order to eliminate any undecomposed propigment and with water in order to wash out any excess of undecomposed diazonium salt. After this treatment the paper was colored blue except in the areas where it had been protected from light by the metal strip.

Example II The procedure of Example I was repeated, except that another diazonium compound was used, namely, the fluoboric acid derivative of diazotized p-aminodiethylanilinc.

Example III The procedure of Example I was repeated except for the diazonium compound which was replaced with diazotized p-aminodiphenylamine and similar results were obtained.

Example IV The procedures of Examples I, II and III were repeated, except that the filter paper was replaced by a high quality paper of photographic grade. Purer blue shades and higher contrasts than in the previous examples were obtained.

Example V A 5% by weight solution of copper phthalocyanine propigment in acetone was mixed with an equal volume of a 1% by weight solution of l-methyl-Z-diethylaminobenzene-S-diazonium fluoborate in acetone and the mixture was coated on a sheet of paper of photographic grade by means of a cotton pad. This operation was carried out in orange light. After drying in the dark, the paper was exposed through a photographic line negative. The lamp arrangement was the same as described in Example I. The exposed paper was Washed with acetone to eliminate any undecomposed propigment and diazonium salt. The resulting positive image was dark blue and had a fairly high contrast.

Example VI Two baryta coated papers of photographic grade were treated with a 2% by weight solution of copper phthalocyanine propigment in acetone and a 2% by Weight solution of diazotized p-aminodiethylaniline in acetone, dried in the dark and exposed to ultraviolet light as in Example I for 5 minutes. One paper (A) was exposed behind a photographic line negative and the other (B) behind a half-tone negative. After exposure both papers were developed with a 10% solution of hydrochloric acid, Washed and dried. Both papers gave a bright blue image on a white background. Print A had satisfactory contrast but print-B appeared rather flat.

Various light sources can be used as the source of radiation. Suitable sources in addition to sunlight include carbon arcs, mercury vapor arcs, fluorescent lamps with special ultraviolet light emitting phosphors, argon glow lamps and photographic flood (incandescent) lamps. These light sources emit light in the range 1800 to 7000 A. and emitan appreciable amount of radiation at wavelengths of 3000 to 4800 A. which are believed to be the most effective wavelengths. They can be used at various distances but generally are used at distances 7 to 20 inches from the surface of the layer to be exposed.

An advantage of the invention is that it provides new photosensitive elements whereby permanent colored images can be obtained. Another advantage is that it provides practical processes for producing photographic images in the form of phthalocyanine pigments, which images are exceptionally fast to light. A further advantage is that the invention is simple and practical and does not require expensive equipment. Still other advantages will be apparent from the above description.

The invention claimed is:

1. A photographic element comprising a sheet support having a layer containing (1) an ethanol-soluble phthalocyanine complex taken from the group consisting of (a) such a complex having the empirical formula M(C H N NH in which each of the six C H N groups represents one phthalonitrile unit, four of which are joined to the central bivalent metal M taken from the group consisting of Cu and Ni and form a metal phthalocyanine molecule, the two extra phthalonitrile units and the extra NH group representing a wing (C H N NH, said complex being further characterized by yielding the corresponding metal phthalocyanine, a phthalonitrile and ammonia upon being treated with reducing agents, (b) such a complex represented by the formula:

R)- MPc\ X- wherein M is a divalent metal taken from the group consisting of Cu and Ni, P0 is a phthalocyanine molecule, R is an alkyl radical, X is a halogen taken from the group consisting of chlorine and bromine and n is a positive integer from 1 to 4 inclusive, (0) such a complex of the formula:

MPO

wherein M is a divalent metal taken from the group consisting of Cu and Ni, Pc is a phthalocyanine molecule and COR is the acyl radical of an organic carboxylic aid of 2 through 7 carbon atoms, and (d) the corresponding metalfree complexes of the complexes (a), (b) and (0) wherein the metal M is replaced by two hydrogen atoms, and (2) a light sensitive diazonium compound which upon exposure to light yields a reducing agent taken from the group consisting of 1,2- and 1,4-aminohydroxybenzene and dihydroxybeuzene.

2. An element as set forth in claim 1 wherein said support is paper.

3. An element as set forth in claim 2 wherein said layer is composed of a water-permeable colloid containing said complex.

4. An element as set colloid is gelatin.

forth in claim 3 wherein said 5. The process which comprises exposing through an image by means of light containing a substantial amount of ultraviolet radiations, a layer containing (1) an ethanol-soluble phthalocyanine complex taken from the group consisting of (a) such a complex having the empirical formula M(C H N NH in which each of the six C H N groups represents one phthalonitrile unit, four of which are joined to the central bivalent metal M taken from the group consisting of Cu and Ni and form a metal phthalocyanine molecule, the two extra phthalonitrile units and the extra NH group representing a wing (C H N NH, said complex being further characterized by yielding the corresponding metal phthalocyanine, a phthalonitrile and ammonia upon being treated with reducing agents, (b) such a complex represented by the formula:

wherein M is a divalent metal taken from the group consisting of Cu and Ni, P0 is a phthalocyanine molecule, R is an alkyl radical, X is a halogen taken from the group consisting of chlorine and bromine and n is a positive integer from 1 to 4 inclusive, (0) such a complex of the formula:

0COR

wherein M is a divalent metal taken from the group consisting of Cu and Ni, P0 is a phthalocyanine molecule and COR is the acyl radical of an organic carboxylic acid of 2 through 7 carbon atoms, and (d) the corresponding metal-free complexes of the complexes (a), (b) and (0) wherein the metal M is replaced by two hydrogen atoms, and (2) a light-sensitive diazonium compound which upon exposure to light yields a reducing agent taken from the group consisting of 1,2- and 1,4- aminohydroxybenzene and dihydroxybenzene; and removing the unreacted complex from the layer.

6. A process as set forth in claim 5 wherein said complex is removed by means of a solvent therefor.

7. A process as set forth in claim 5 wherein said complex is removed by means of an aqueous solution containing an acid.

8. A process as set forth in claim 5 wherein said complex is removed by means of an aqueous solution containing a strong non-oxidizing mineral acid.

9. A process as set forth in claim 5 wherein said image is a continuous tone negative image.

References Cited in the file of this patent UNITED STATES PATENTS 1,876,052 Haendel Sept. 6, 1932 2,193,574 Tendeloo Mar. 12, 1940 2,623,821 Isherwood Dec. 30, 1952 2,683,643 Baumann et a1. July 13, 1954 

1. A PHOTOGRAPHIC ELEMENT COMPRISING A SHEET SUPPORT HAVING A LAYER CONTAINING (1) AN ETHANOL-SOLUBLE PHTHALOCYANINE COMPLEX TAKEN FROM THE GROUP CONSISTING OF (A) SUCH A COMPLEX HAVING THE EMPIRICAL FORMULA M(C8H4N2)LNH IN WHICH EACH OF THE SIX C8H4N2 GROUPS REPRESENTS ONE PHTHALONITRILE UNIT, FOUR OF WHICH ARE JOINED TO THE CENTRAL BIVALENT METAL M TAKEN FROM THE GROUP CONSISTING OF CU AND NI AND FORM A METAL PHTHALOCYANINE MOLECULE, THE TWO EXTRA PHTHALONITRILE UNITS AND THE EXTRA NH GROUP REPRESENTING A WING (C8H4N)2NH SAID COMPLEX BEING FURTHER CHARACTERIZED BY YIELDING THE CORRESPONDING METAL PHTHALOCYANINE,A PHTHALONITRILE AND AMMONIA BEING TREATED WITH REDUCING AGENTS, (B) SUCH A COMPLEX REPRESENTD BY THE FORMULA: 